The zodiac, a symbolic reference to cyclic time, is one of the most elevated elements related to the sun and the celestial sphere. The accurate surveys carried out recently have shown that the zodiacs of the Baptistry of San Giovanni and of the Basilica of San Miniato al Monte in Florence not only have a decorative purpose, but they were also built with a precise astronomic function: on the day of the summer solstice, a ray of light still today illuminates the sign of the Cancer on the marble zodiac of San Miniato and such an event makes it the oldest monumental solstice zodiac that is still in working order, in Europe.